I updated my computer to Windows 10 and lost some files, how can I get them back?

I updated my computer to Windows 10. Everything was fine, my files were packed in one folder and I easily found them and put them on my desktop. Unfortunately, I didn't realize that the installation wasn't over. The same day it continued and the next day I discovered that my files (ones on the desktop) disappeared. I can't find them anywhere. The names still appear in some places but i can't really access them.